Shoreline erosion is a growing concern for those who live in coastal areas. Many beaches today are losing shoreline at a rate of 2-6 feet per year. Severe weather patterns exacerbate this issue, and can result in the loss of large portions of shoreline in a very brief time. It has been predicted by some that the severity of the weather will increase in the coming years, making this issue even more important. The loss of shoreline has a detrimental impact on property values, since property may be difficult to sell when there is a chance that erosion will eventually cause the property to become unlivable. Also, sudden erosion due for example to a storm can also pose a danger to those residing in such areas.
Loss of shoreline also negatively impacts coastal marine organisms living in these areas, since marine life, especially coastal marine life, may become buried and die off. Marine life is also affected when coastal erosion causes contaminants such as oil to be released into the water.
Existing methods of controlling beach erosion include building retention walls, groins, and revetments to impede the erosion process. Retention walls are large structures which are designed to stop high tides from hitting the beach, generally running parallel to the shoreline and located hundreds of feet out into the sea. Groins are structures that extend into the ocean from the beach and are oriented perpendicularly to the shoreline. Whereas a retention wall typically stands alone, groins tend to be used in conjunction with many other groins, and are typically placed at substantially regular intervals along the length of the beach. They function by trapping sand that is pulled at an angle from the beach by cross currents, and would otherwise be pulled out to sea by the tide. Revetments are man-made structures placed on slopes at the water's edge that are designed to absorb the impact of the tides.
These methods of controlling erosion all cause sediment deposits to occur, and do not prevent the removal of sand from other areas of the beach. These methods also cause destruction of shoreline vegetation, further destabilizing the shoreline.
Other methods of shoreline erosion control include construction of jetties and bulkheads, building of sand dunes and growing of vegetation on and around them, and adding additional sand to the beach periodically to counteract the effects of erosion that has already occurred.
Bulkheads are substantially vertical structures, whose heights are generally several times taller than their widths, with lengths that run parallel to, and the length of, the coastal land that is to be protected from erosion. They are made of a material of sufficient strength to resist the impact of the tide. They are generally used for providing stability to steep slopes, and are thus not suitable for preventing erosion of the beach front itself, but can help prevent erosion from extending landward from the beach front.
Jetties are long structures, generally employed in pairs, which extend substantially perpendicularly from the shoreline and are built at the mouths of inlets. They are mainly designed to push sediment further from the mouth of the inlet, where deeper waters make this less of an issue. As a side benefit, they also trap sand and provide some measure of beach erosion control to adjacent areas, by reducing the effects of along-shore drift. This however, causes the same issue of destroying shoreline vegetation as previously discussed measures.
Addition of sand on a periodic basis can be expensive and difficult, and also causes burial and destruction of shoreline vegetation. Construction of sand dunes and growing of vegetation around them provides an aesthetically pleasing and effective method of controlling shoreline erosion, but the vegetation must be planted and cared for during the critical first few months, to ensure that the project is successful. Such freshly planted vegetation is also not as robust as mature or semi-mature vegetation, and is more likely to perish if conditions become harsh before the vegetation has a chance to grow and strengthen itself. This limits the time periods when this technique can be utilized, since the vegetation must be planted at a time when conditions can be expected to remain ideal long enough for the vegetation to mature.
Typical sod has been around for quite some time, and allows for growth of grass seedlings offsite and transportation of the mature or semi-mature grass, along with its root structure and soil, to another site, where it can be quickly incorporated into the existing landscape. Traditional sod would not be suitable for a beach environment, where it would be exposed to sand and salt on a regular basis.
Currently, there exists a coir mat that contains un-sprouted sea grass seeds. This coir mat is used to control erosion of steep hills, such as those near roadways. Although this is a durable, biodegradable, and aesthetically appealing solution, it does not alleviate the issue of extended maintenance and care until the vegetation eventually becomes self-sustaining.
Coir mats with traditional grass pre-grown therein is sometimes used as an “instant lawn.” However, this approach would not be suitable for use in a saltwater environment, since the grass would not thrive in sand, and would not tolerate extended exposure to salt.
What is needed, therefore, is a method for introducing self-sustaining, shoreline-tolerant vegetation to coastal areas so as to minimize the impact of erosion on the shoreline and its ecosystem, without requiring an initial maintenance period, and without introducing permanent, artificial structures into the environment.